Water resistant inorganic nitrate based explosive composition



United States Patent Ofilice 3,326,734 WATER RESESTAN'K HNORGANHZNETRATE BASED EXiLOSlVE COMPOSII'KEON Thomas E. Slylrhouse, Midland,Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporationof Delaware No Drawing. Filed dune 29, 1966, Ser. No. 561,324

Claims. (Cl. 149-41) ABSTRAKIT OF THE DESCLOSURE An explosivecomposition comprising a particulate inorganic oxidizer, preferablyammonium nitrate, a substantially saturated aqueous solution ofmagnesium nitrate, ammonium nitrate or an aqueous animoniacal ammoniumnitrate solution and setting agent which sets the composition to a solidmaterial Which contains the solvent used in the liquid phase. Thesecompositions have a relatively high density and are water resistant.

This application is a continuation-in-part of application Ser. No.355,926 filed March 30, 1964, now abandoned.

This invention relates to inorganic based explosives and moreparticularly is concerned With a novel Water resistant inorganic nitratebased explosive composition.

It is a principal object of the resent invention to provide an explosivesystem which sets up into a hard, dense mass.

It is another object of the present invention to provide an explosivecomposition having a density greater than 1 gram per cubic centimeterand which has good sensitivity to shock initiation and delivers highquantities of working energy upon detonation.

It is also an object of the present invention to provide a novel,relatively dense inorganic based explosion composition that exhibitsgood resistance to degradation by Water.

These and other objects and advantages readily will become apparent fromthe detailed description presented hereinafter.

In general the present novel composition comprises a particulateinorganic oxidizer, a substantially saturated solution selected from thegroup consisting of aqueous magnesium nitrate, aqueous ammonium nitrateand aqueous ammoniacal ammonium nitrate and a setting agent which setsthe explosive composition to a solid material containing solvent used inthe liquid phase. One embodiment of the present novel inventioncomprises from about 40 to about 75 parts by Weight particulate ammoniumnitrate, from about to about 35 parts by Weight of an aqueous solutionof magnesium nitrate or ammonium nitrate or an aqueous ammoniacalsolution of ammonium nitrate and a minimum of about 2 parts by weight ofcertain specific inorganic salts or oxides as setting agent. Ordinarilyfrom about 2 to about 10 parts by weight or more of the setting agentare used. Preferably the present novel explosive composition comprisesfrom about 50 to about 70 parts by Weight prilled or granular ammoniumnitrate, from about 22 to about 28 parts by weight of the saturatedaqueous magnesium nitrate or ammonium nitrate solution or saturatedaqueous ammoniacal 35,325,73d Patented June 20, Mid? ammonium nitratesolution and from about 4 to about 8 parts by weight magnesium oxide assetting agent.

Suitable inorganic oxides or salts for use in the present composition assetting agents are those materials which will dissolve or react With anyammoniacal or aqueous nitrate solution to set the composition to a solidmaterial Which contains the solvent used in the liquid phase. Preferablythese materials react over a period of time and do not react with wateror ammonia in a highly exothermic manner with rapid release of largequantities of heat. Illustrative examples of inorganic metal oxides andinorganic metal salts suitable for use as setting agents are thealkaline earth metal oxides (i.e., calcium oxide, strontium oxide,barium oxide and magnesium oxide), zinc oxide, lead monoxide, calcineddolomitic limestone (i.e., a mixture of calcium oxide and magnesiumoxide) and the substantially anhydrous salts, calcium sulfate, sodiumsulfate, magnesium sulfate, sodium tetrapyrophosphate and sodiumthiosulfate. Magnesium oxide has been found to be particularlyeffective. The setting agents can be used alone or mixtures of these canbe employed.

The actual amount of setting agent to be employed is dependent to someextent on the Water resistivity and sensitivity desired in thecomposition. As the amount of setting agent increases, the Waterresistivity of the final composition increases and the sensitivitydecreases. This latter effect is particularly evidenced in thecompositions containing the larger amounts, e.g., 15-Z0 percent or moreof setting agent. Ordinarily this agent is used in finely divided form.Commercially available powdered materials, such as oxychloride grademagnesite (MgO), usually are used since these provide the requiredreactivity to promote the setting reaction of the composition atrelatively low concentrations.

Ordinarily the aqueous solutions of magnesium nitrate or ammoniumnitrate are prepared by dissolving the corresponding solute member inthe appropriate solvent either at room temperature or at elevatedtemperatures. Conveniently, commercially available aqueous ammoniacalsolutions saturated with respect to the ammonium nitrate solute at aboutroom temperature and containing from about 6 to about 15 percent watercan be used as the ammonium nitrate solution component of thecomposition.

Both unsaturated and saturated solutions of the nitrate material andeutectic solutions containing the nitrate component in combination withother materials can be employed.

If desired, other fuel components such as particulated light metals,e.g., aluminum, aluminum alloys, magnesium, magnesium alloys and thelike can be incorporated into the present composition in an amount up toabout 50 parts by weight. The particulation of the light metal is notcritical. Relatively large particles have been found to be quitesuitable. Conveniently, these are readily available as commercial scrapflakes, chopped foil, machine chips, shavings, turnings and the like.

Organic materials such as alcohols, urea, nitrocarbonitrates,conventionally explosives, sugars, hydrocarbon, etc. also can bedissolved in or otherwise incorporated into or carried in thecomposition as sensitizers and/or fuels.

Other particulate inorganic oxidizers can be used to A standardlead-block deformation sensitivity test was replace at least a portionof the solid ammonium nitrate used. In this test, 100 g. charges wereprepared in 1.5 component. Representative examples of such oxidizersinch diameter small plastic bottles, the final set mix are ammoniumperchlorate, potassium nitrate, barium occupying about 0.6 of the volumeof the bottle. nitrate and sodium nitrate. 5 A strand of 200 grain perfoot Primacord encased in In preparing the present novel composition,usually a glass tube was inserted down through the center of the solidparticulate oxidizer is blended with the setting the charge as it wasfirst prepared, the final product thus agent, e.g. magnesium oxide,(along with other solid setting up around the Primacord initiator. Thebottle concomponents if such are employed) and the saturated taining theso-primed charge was positioned on a A- nitrate solution and any otherliquid components then inch thick steel plate which in turn was centeredon 21 added to this mixture. As first prepared, the composilead block inthe shape of a regular prism having a 1 ion rang s in consistency fr aViSCOUS Paste a inch by 1 inch square base and being about 2 incheshigh. pourable slurry depending upon the amount of solution This leadblock was centered on top of a /2-inch thick used. The mix is placed ina suitable cardboard, plastic, steel plate about 6 inches on a side.wooden, metal or other liquid resistant mold r n- The Primacordinitiator was activated by a No. 6 tainer and allowed to stand for apredetermined period electric blasting cap. The deformation, i.e.reduction in of time, usually from about 18 to 24 hours or m re. heightof the lead block from detonation of the charge During this period themix Cures, i.e. s ts, t a gave a measurement of the sensitivity of theproduct. dense compact mass. An advantage f the pr s t C Table IIpresents charge data and results for a number position is that it can becast into any of a wide variety of compositions of shapes or formsthereby giving a final explosive charge of predetermined shape for anyof a number or specific TABLE H uses.

The following examples will serve to further illustrate the presentinvention but are not meant to limit it thereto. 25 Charge composltlon(parts by Weight) Lead Block Example .-A number of explosivecompositions were gig} Particulate Saturated a i gg g fi? prepared usingan oxychloride grade magnesite, aqueous Ammonium Mg NO3 l MgO Alsaturated magnesium nitrate or aqueous ammoniacal Nitrate Solutionsaturated ammonium nitrate solution and particulate prilled ammoniumnitrate. Additionally, some of the ii g fg ggg ffi Nitmemntmn 5 mixesalso had particulate aluminum fuel incorporated 70 6 5 therein. Eachcomposition was fabricated by adding the gg gg i 2 5 solution to asubstantially homogeneous blend of the g3 27 3.6 10 15 solid materials,casting this into a cylindrical cardboard 2: 2? f mold and curing theso-cast structure at ambient room 67 25 2 15 0.5 temperature for about24 hours. The mold had a cylindrical projection jutting upward from itsbottom thus Oxychloride grade. making a corresponding depression in oneend of the 2 5 25 1 3? uminum 011 of thickness about 0.001 inch andabout Me charge to accommodate a detonator. 3 Aluminum curled turningsabout M32 to Moinchinthiclmess, iainch i 1,, For detonation studies, thecured charge was primed inwldth and abmtAmAmmmlength with a commerciallyavailable /5-pound high explosive booster inserted in the depression.The so-primed charge was positioned in a bore hole in a sandy soil anddet- Example number f studies w r m e to ev luate the elfectiveness ofsetting agents with aqueous amonated.

Table I which follows presents charge composition monium nitratesolutions. In these studies, a predeterdata for a number of differentcompositions. mined amount of setting agent was mixed with a pre- TABLEI Satd Mg(N Oi); Ammonium Qharge Mix Ammonium Solution, Nitrate MgO A1Diameter, No. Nitrate Weight per- Solution 1 in.

cent

1 65.5% NHiNO5, 28% NHi, 6.5% H20.

2 Chopped [oil of about 0.001 inch thickness and about Ms inch square.

3 1 part by Weight chopped foil and 6 parts by Weight atomized pelletsto 100 mesh U.S. Standard Sieve.

These mixes propagated and gave evidence of complete determined quantityof aqueous ammonium nitrate soludetonation with production of usefulexplosive power tion (solution contains about 63 percent by weight amasdemonstrated by earth movement and cratering. monium nitrate). After thesetting agent had been mixed Example 2.A number of small sized charges(-l00 with the ammonium nitrate solution, the reaction mass grams) wereprepared following the same general prowas allowed to stand for a periodof time and the setting cedure described in Example 1 and theirsensitivity to characteristics noted. Table III which follows summarizesdetonation evaluated. 1 the data obtained in this study.

TABLE III Setting Agent Ammonium Run No. Nitrate Remarks Solution (g.)Type Amount (g.)

1 CaO 1 1 1 Mix set up rapidly with some heating into a strong, hardmass.

2 MgO 1 1 1.4 Original mixture was paste-like with no evidence ofheating. Good mix waipb'tained which after 24 hours was in the form of avery hard, strong cas ing.

3 MgO 2 1 1.2 Initial mix was paste-like which after 24 hours was in theform of a very hard, especially strong casting.

4 Na lzO (anh.) 1 0. 85 Slurry formed upon initial mixing which began toharden quickly. Set up to a weal: solid in about 5-10 minutes. Solidproduct was very strong and hard after 24 hours.

5 NBJSOJ (anh.) 1 0.3 Crystals moistened with little indication of areaction. Hard, moderately strong solid casting formed.

6 PbO 1.14 0. 42 Reacted very quickly and formed a Wet-crumbly solid.

7 ZnO 1 1 Mixture formed a fluid paste. Set up overnight into a hard,very strong casting.

8 Drierite (anh.) CaSOi 1 1 Mix began to thicken and harden very soonafter mixing and set into a hard mass after standing overni ht.

9 Nagsgos (anh.) l 0. 37 Set to fairly hard mass in about 1 minute withlittle stirring. Solid product was very hard after 24 hours.

10 CaSOi (anh.) 3 1 2 Mix started to set in about 5 minutes. Afterstanding 24 hours product was a very hard, strong mass.

1 Reagent grade. 1 Oxyohloride grade.

In a manner similar to that described for the foregoing examples, dense,set, water resistant explosive compositions can be prepared usingsaturated ammonium nitrate solution, magnesium oxide and particulateammonium nitrate. Likewise other setting agents set forth hereinbeforecan be used in conjunction with the other disclosed liquid and so idcomponents to prepare dense water resistant explosive compositions.

Various modifications can be made in the present invention withoutdeparting from the spirit or scope thereof for it is understood that Ilimit myself only as defined in the appended claims.

I claim:

1. An explosive composition which comprises:

(a) from about 40 to about 75 parts by weight particulate ammoniumnitrate,

(b) from about to about parts by weight of a solution selected from thegroup consisting of aqueous magnesium nitrate, aqueous ammonium nitrateand aqueous ammoniacal ammonium nitrate, and

(c) at least about 2 parts by Weight of a setting agent member selectedfrom the group consisting of alkaline earth metal oxides, zinc oxide,lead monoxide, calcined dolomitic limestone, substantially anhydrouscalcium sulfate, substantially anhydrous magnesium sulfate,substantially anhydrous sodium tetra-pyrophosphate and substantiallyanhydrous sodium thiosulfate, said member being further characterized insetting said composition to a solid material which contains solvent usedin the liquid phase.

2. The composition as defined in claim 1 wherein the setting agent is analkaline earth metal oxide and is characterized in that it reacts withthe solvent of the nitrate solution over a period of time and sets saidcomposition to a solid containing said solvent member.

3. The explosive composition as defined in claim 2 wherein the settingagent is magnesium oxide.

4. The explosive composition as defined in claim 2 and having up toabout 50 parts by weight of a particulated light metal.

5. The explosive composition as defined in claim 2 which comprises:

(a) from about 50 to about 70 parts by weight prilled ammonium nitrate.

(b) from about 22 to about 28 parts by weight of a substantiallysaturated solution selected from the group consisting of aqueousmagnesium nitrate, aqueous ammonium nitrate and aqueous ammoniacalammonium nitrate, and

(c) from about 4 to about 8 parts by weight magnesium oxide to effectsolidification of said composition.

6. The explosive composition as defined in claim 5 3 2.25 grams ofcrushed NHrNOa prills also incorporated into this mix.

and having from about 2 to about 25 parts by weight of particulatedaluminum.

'7. A method for preparing a dense, water-resistant inorganic basedexplosive composition which comprises:

(a) blending from about 40 to about 75 parts by weight solid particulateammonium nitrate with at least about 2 parts by weight of a memberselected from the group consisting of alkaline earth metal oxides, zincoxide, lead monoxide, calcined dolomitic limestone. sub tantiallyanhydrous calcium sulfate, substantia ly anhydrous magnesium sulfate,substantially anhydrou sodium tetrapyrophosphate and substantiallyanhydrous sodium thiosulfate, said member being further characterized insetting said composition to a solid material which contains solvent usedin the 40 liquid phase of a solution selected from the group consistingof aqueous magnesium nitrate, aqueous ammonium nitrate and aqueousammoniacal ammonium nitrate,

(b) adding to the resulting blend from about 20 to about 35 parts byweight of a solution selected from the group consisting of aqueousmagnesium nitrate, aqueous ammonium nitrate and aqueous ammoniacalammonium nitrate,

(c) mixing the liquid and solid components to provide a substantiallyhomogeneous composition,

(d) curing said composition at ambient temperature for a period of fromabout 12 to about 24 hours thereby to provide a dense, set, waterresistant explosive composition.

8. The process as defined in claim 7 employing from about 50 to about 70parts by weight prilled ammonium nitrate and from about 4 to about 8parts by weight magnesium oxide to provide the initial blend of solidsand having from about 22 to about 28 parts by weight of a substantiallysaturated solution selected from the group consisting of aqueousmagnesium nitrate, aqueous ammonium nitrate and aqueous ammoniacalammonium nitrate mixed therewith.

9. The process as defined in claim 7 and including the step ofincorporating up to about 50 parts by weight of a particulated lightmetal into the initial blend of solids.

10. In an explosive composition comprising a particulate inorganicoxidizer selected from the group consisting of ammonium nitrate,ammonium perchlorate, potassium nitrate, barium nitrate, sodium nitrateand mixtures thereof and a substantially saturated solution selectedfrom the group consisting of aqueous magnesium nitrate, aqueous ammoniumnitrate and aqueous ammoniacal ammonium nitrate, the improvement whichcomprises blending into said explosive composition at least about 2parts by weight of a setting agent selected from the group con- 7 8sisting of alkaline earth metal oxides, zinc oxide, lead ReferencesCited monoxide, calcined dolomitic limestone, substantially an hydrouscalcium sulfate, substantially anhydrous magnesium sulfate,substantially anhydrous sodium tetrapyro- 3,212,944 10/1965 Lyon et a1149-2 X phosphate and substantially anhydrous sodium thiosul- 53,266,960 8/1966 Lyon at fate, said setting agent being characterized insetting said explosive composition to a'solid material which containsCARL QUARFORTH Primary Examiner solvent used in the liquid phase. L. A.SEBASTIAN, Assistant Examiner

1. AN EXPLOSIVE COMPOSITION WHICH COMPRISES: (A) FROM ABOUT 40 TO ABOUT75 PARTS BY WEIGHT PARTICULATE AMMONIUM NITRATE, (B) FROM ABOUT 20 TOABOUT 35 PARTS BY WEIGHT OF A SOLUTION SELECTED FROM THE GROUPCONSISTING OF AQUEOUS MAGNESIUM NITRATE, AQUEOUS AMMONIUM NITRATE ANDAQUEOUS AMMONIACAL AMMONIUM NITRATE, AND (C) AT LEAST ABOUT 2 PARTS BYWEIGHT OF A SETTING AGENT MEMBER SELECTED FROM THE GROUP CONSISTING OFALKALINE EARTH METAL OXIDES, ZINC OXIDE, LEAD MONOXIDE, CALCINEDDOLOMITIC LIMESTONE, SUBSTANTIALLY ANHYDROUS CALCIUM SULFAE,SUBSTANTIALLY ANHYDROUS MAGNESIUM SULFATE, SUBSANTIALLY ANHYDROUS SODIUMTETRAPYROPHOSPHATE AND SUBSTANTIALLY ANHYDROUS SODIUM THIOSULFATE, SAIDMEMBER BEING FURTHER CHARACTERIZED IN SETTING SAID COMPOSITON TO A SOLIDMATERIAL WHICH CONTAINS SOLVENT USED IN THE LIQUID PHASE.